Zinc phosphide treated oats is one of the most common agricultural rodenticides available. Zinc phosphide is an acute toxicant that kills a rodent within 12- to 24-hours of ingesting it. Upon ingestion, the zinc phosphide meets the rodent’s stomach acids liberating phosphine gas.
Phosphine gas is the same active ingredient found in aluminum phosphide pellets/tablets used to control insects in grain bins. The exact way phosphine gas kills the rodent is unclear. But one theory is that it interferes with heart function.
One advantage of zinc phosphide treated oats is that there is effectively zero secondary poisoning. Animals that feed upon animals poisoned with zinc phosphide do not get poisoned. There is, however, one exception. If the predator or scavenging animal eats undigested zinc phosphide treated oats, such as those that might be in the cheek pouches of a rodent, then poisoning can occur. But that situation is actually a form of primary poisoning not secondary poisoning.
If you look at the photo at the right, you will see that zinc phosphide treated oats has a grayish coloration. That is because the oats are treated with an oil and then mixed with the zinc phosphide powder. The oil allows the zinc phosphide to adhere to the exterior of the grain. In contrast untreated oats, has a yellow coloration.
Zinc phosphide treated oats is an important tool for the managing of agricultural rodent pests. However, to use it more effectively keep the following principles in mind.
- Follow the label. Seriously, the label helps you use the product in an effective manner.
- Use when rain is not in the forecast. Zinc phosphide can be washed off or otherwise, removed from the grain by water, so use when conditions are dry.
- If the label says pre-bait, then pre-bait. Zinc phosphide is bitter. Pre-baiting conditions the rodents to feed on the grain so that when they see it again, they gobble it rather than taste it, thereby ensuring a lethal dose.